From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from localhost.localdomain (unknown [147.136.157.0]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 7569030CD88; Thu, 23 Oct 2025 12:54:59 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=147.136.157.0 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761224101; cv=none; b=a83oZPxyYn5+J4/ME404qoJ0FAeBBfbhE2RF+KCd3B85oTCjZ8nttnbXAHtNbn4ToZYjIIP0bw0jeIbHbD8zLC3EtdsmPmIYh7v2KYJaVN76455qhUvlafhGfBWn7jeKNUH36T1vCUsdZGixiuvxGezOrPuLc+5c6+rqqNuIFQ0= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1761224101; c=relaxed/simple; bh=7+HBsezobnLBCgzcgo/KsuyWscdJ+R6h13UrMG8hrVg=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=SK4VYwCorEA2JeXwiW1rN+L0QJauglYSqgF7h1n9NAqTeRObnEdZaC0WsF30WqIG2lq32M4ty+zGEjr23xEO5Q5RGLpnuDpYdoox8cG+GaIfmjAzNLAa6mPT8wQc/gIxc5+ftM3ajT3+fF0FiEUxn4PMm32tUVTmwC3VBcuMG2o= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev; spf=none smtp.mailfrom=localhost.localdomain; arc=none smtp.client-ip=147.136.157.0 Authentication-Results: smtp.subspace.kernel.org; dmarc=fail (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=none smtp.mailfrom=localhost.localdomain Received: by localhost.localdomain (Postfix, from userid 1007) id 7E40D9291F4; Thu, 23 Oct 2025 20:54:52 +0800 (+08) From: Jiayuan Chen To: mptcp@lists.linux.dev Cc: Jiayuan Chen , John Fastabend , Jakub Sitnicki , Eric Dumazet , Kuniyuki Iwashima , Paolo Abeni , Willem de Bruijn , "David S. Miller" , Jakub Kicinski , Simon Horman , Matthieu Baerts , Mat Martineau , Geliang Tang , Alexei Starovoitov , Daniel Borkmann , Andrii Nakryiko , Martin KaFai Lau , Eduard Zingerman , Song Liu , Yonghong Song , KP Singh , Stanislav Fomichev , Hao Luo , Jiri Olsa , Shuah Khan , Florian Westphal , linux-kernel@vger.kernel.org, netdev@vger.kernel.org, bpf@vger.kernel.org, linux-kselftest@vger.kernel.org Subject: [PATCH net v3 0/3] mptcp: Fix conflicts between MPTCP and sockmap Date: Thu, 23 Oct 2025 20:54:31 +0800 Message-ID: <20251023125450.105859-1-jiayuan.chen@linux.dev> X-Mailer: git-send-email 2.43.0 Precedence: bulk X-Mailing-List: bpf@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit Overall, we encountered a warning [1] that can be triggered by running the selftest I provided. MPTCP creates subflows for data transmission between two endpoints. However, BPF can use sockops to perform additional operations when TCP completes the three-way handshake. The issue arose because we used sockmap in sockops, which replaces sk->sk_prot and some handlers. Since subflows also have their own specialized handlers, this creates a conflict and leads to traffic failure. Therefore, we need to reject operations targeting subflows. This patchset simply prevents the combination of subflows and sockmap without changing any functionality. A complete integration of MPTCP and sockmap would require more effort, for example, we would need to retrieve the parent socket from subflows in sockmap and implement handlers like read_skb. If maintainers don't object, we can further improve this in subsequent work. [1] truncated warning: [ 18.234652] ------------[ cut here ]------------ [ 18.234664] WARNING: CPU: 1 PID: 388 at net/mptcp/protocol.c:68 mptcp_stream_accept+0x34c/0x380 [ 18.234726] Modules linked in: [ 18.234755] RIP: 0010:mptcp_stream_accept+0x34c/0x380 [ 18.234762] RSP: 0018:ffffc90000cf3cf8 EFLAGS: 00010202 [ 18.234800] PKRU: 55555554 [ 18.234806] Call Trace: [ 18.234810] [ 18.234837] do_accept+0xeb/0x190 [ 18.234861] ? __x64_sys_pselect6+0x61/0x80 [ 18.234898] ? _raw_spin_unlock+0x12/0x30 [ 18.234915] ? alloc_fd+0x11e/0x190 [ 18.234925] __sys_accept4+0x8c/0x100 [ 18.234930] __x64_sys_accept+0x1f/0x30 [ 18.234933] x64_sys_call+0x202f/0x20f0 [ 18.234966] do_syscall_64+0x72/0x9a0 [ 18.234979] ? switch_fpu_return+0x60/0xf0 [ 18.234993] ? irqentry_exit_to_user_mode+0xdb/0x1e0 [ 18.235002] ? irqentry_exit+0x3f/0x50 [ 18.235005] ? clear_bhb_loop+0x50/0xa0 [ 18.235022] ? clear_bhb_loop+0x50/0xa0 [ 18.235025] ? clear_bhb_loop+0x50/0xa0 [ 18.235028] entry_SYSCALL_64_after_hwframe+0x76/0x7e [ 18.235066] [ 18.235109] ---[ end trace 0000000000000000 ]--- --- v2: https://lore.kernel.org/bpf/20251020060503.325369-1-jiayuan.chen@linux.dev/T/#t Some advice suggested by Jakub Sitnicki v1: https://lore.kernel.org/mptcp/a0a2b87119a06c5ffaa51427a0964a05534fe6f1@linux.dev/T/#t Some advice from Matthieu Baerts. Jiayuan Chen (3): net,mptcp: fix proto fallback detection with BPF sockmap bpf,sockmap: disallow MPTCP sockets from sockmap selftests/bpf: Add mptcp test with sockmap net/core/sock_map.c | 27 ++++ net/mptcp/protocol.c | 9 +- .../testing/selftests/bpf/prog_tests/mptcp.c | 150 ++++++++++++++++++ .../selftests/bpf/progs/mptcp_sockmap.c | 43 +++++ 4 files changed, 227 insertions(+), 2 deletions(-) create mode 100644 tools/testing/selftests/bpf/progs/mptcp_sockmap.c -- 2.43.0